Hydrograph, Flood

Synonyms

Flood time–discharge relationship; Flood wave; Storm hydrograph

Definition

The hydrograph is the plot of water-flow discharge (runoff) versus time at a given river station (where a flow gauge might be located). The storm hydrograph represents the discharge record of river flow during extreme events, as the flood volume exceeds the maximum conveyance capacity of the river channels (see also Flood Stage) and the floodwaters – overtopping the banks – propagate through the floodplain (see entry Floodplain).

Discussion

The flood hydrograph is indirectly linked to a wide range of heterogeneous, spatially distributed factors pertaining to the upstream areas of the watershed. Those factors include the climatic, hydrologic, geomorphologic, geologic, hydraulic, and ecological conditions that, together with artificial features (e.g., levees, reservoirs, bridges, etc.), characterize the flood generation, propagation, and inundation phenomena, and range from the hydrologic forcing...